The present invention concerns methods and apparatus for a data communications security system. More particularly the present invention is concerned with a data communication system having a security data processing station remote from both the central station and the local user stations.
There are a number of different data communication systems providing means for security control, that is apparatus for monitoring the status of various alarm devices and periodically providing data concerning the status of the devices to a central computer station. A typical security system includes a central station communicating with a number of remote user stations by coaxial cable. Typically, each user station includes several security monitoring devices such as a smoke detector and door and window switches. Additional emergency buttons may be included at the user station to summon police, firemen or medical assistance. These devices provide alarm signals to a home terminal which converts the signals to a format compatible for transmission over the coaxial cable to the central computer station. It is also common to combine such a security system with a cable television system.
One of the difficulties experienced with this conventional approach is the expense involved in providing a complete home terminal at each remote user station. Such a terminal normally includes an arming control station, a receiver-transmitter modem and substantial processing logic in order to process the alarm signals and transmit them in a format acceptable to the central computer station. The cost of purchasing, installing and maintaining such a home terminal system has been prohibitive for many otherwise potential subscribers.
In addition to the foregoing difficulty, the location of a complete security terminal at the location where security is being monitored increases the likelihood of disruption of the system by tampering. In fact, the potential for tampering by an intruder effectively defeats one purpose of the system in warning of intrusion and burglary. Moreover, the presence of a terminal at the remote user location offers an opportunity for a user to tamper with his own teminal in an attempt to change his level of service from that authorized by the central station. This is a particular problem where a cable security system is coupled with a subscription television system providing different levels of television service to the user.